KR20220125182A - Method for manufacturing multi-tone photomask, and multi-tone photomask - Google Patents

Abstract

A method for manufacturing a multi-gradation photomask that does not require alignment and a multi-gradation photomask are provided. The method of manufacturing a multi-gradation photomask comprises the steps of: preparing an intermediate body in a structure of laminates having a semi-transmissive film (3) stacked on a transparent substrate (2), an intermediate film (4) having an etching characteristic different from the etching characteristics of the semi-transmissive film (3) and stacked on the semi-transmissive film (3) to overlap the semi-transmissive film (3) and a light-shielding film (5) having the same etching characteristics as the semi-transmissive film (3) and laminated on the intermediate film (4) such that at least a part of a peripheral region of the intermediate film (4) is exposed wherein at least a portion of the exposed part of the intermediate film (4) has a shape in which an edge (4a) spreads outward coming closer to the transparent substrate (2); finally removing the exposed part of the intermediate film (4) by dividing a plurality of times and etching the same; and changing the transmittance of the exposed part by plasma processing the exposed part of the semi-transmissive film (3) after each round of etching that excludes or includes the final round. The present invention is to realize the high precision of a multi-gradation photomask without misalignment.

Description

The manufacturing method of a multi-gradation photomask, and a multi-gradation photomask TECHNICAL FIELD

The present invention relates to a method for manufacturing a multi-gradation photomask having a gradation portion, and to a multi-gradation photomask.

The multi-gradation photomask includes (includes) a semi-transmissive portion having a transmittance between the transmittance of the transmitting portion and the transmittance of the light-shielding portion. Multiple gradations (three or more gradations) are realized by adding the gradations in the middle of black (gray tones). By using a multi-gradation photomask, it is possible to form a pattern in a photoresist with different exposure amounts in one exposure. For this reason, reduction of the number of sheets used of a photomask, reduction of a manufacturing process, and also reduction of manufacturing cost can be aimed at.

As a kind of multi-gradation photomask, there is a gradation mask. A gradation mask is a photomask provided with a gradation part (patent document 1). The gradation portion is composed of a plurality of regions having different transmittances. More specifically, the gradation part is provided (installed or formed) in the boundary region between the transflective part and the transmissive part in the transflective part, and is composed of a plurality of regions in which the transmittance is gradually increased toward the boundary between the transflective part and the transmissive part.

[Patent Document 1] Japanese Patent Laid-Open No. 2011-209759

The conventional method for manufacturing a gradation mask requires at least two drawing steps: a drawing step (exposure step) of a pattern constituting a light-shielding portion and a drawing step of a pattern constituting a semi-transmissive portion. And when the drawing process becomes multiple times (several times), it will become easy to generate|occur|produce the position shift (alignment shift) of the pattern formed in each process.

As a countermeasure against this, there is the use of an alignment mark. The drawing process after the 2nd time WHEREIN: It is that alignment (alignment) is performed by reading an alignment mark. However, even if an alignment mark is used, it is impossible to completely eliminate an alignment shift, and an alignment shift of 500 nm at most will generate|occur|produce. For this reason, it has become a situation where it is difficult to make high-definition multi-gradation photomask.

Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for manufacturing a multi-gradation photomask and a multi-gradation photomask capable of realizing high-definition multi-gradation photomasks without misalignment.

A method of manufacturing a multi-gradation photomask according to the present invention,

A method of manufacturing a multi-gradation photomask, comprising: a transmissive part, a semi-transmissive part, and a light-shielding part;

A semi-transmissive film having a predetermined pattern shape and laminated on a transparent substrate, an intermediate film having an etching characteristic different from that of the semi-transmissive film and stacked so as to overlap the semi-transmissive film, and a predetermined pattern shape and etching characteristics identical to those of the semi-transmissive film, An intermediate comprising a light-shielding film laminated on the intermediate film so that at least a portion of the peripheral region of the intermediate film is exposed, and having a shape in which the edge spreads outward as at least a part of the exposed portion of the intermediate film approaches the transparent substrate; An intermediate preparation process to prepare, and

an intermediate film division etching process in which the exposed portion of the intermediate film is divided into a plurality of times and etched to be finally removed;

After each etching except the last time or including the last time, plasma treatment of the exposed portion of the semi-permeable film, and a plasma treatment step of changing the transmittance of the portion

A method of manufacturing a multi-gradation photomask.

In addition, the multi-gradation photomask according to the present invention,

A multi-gradation photomask having a transmissive part, a semi-transmissive part, and a light-shielding part, comprising:

A semi-transmissive film having a predetermined pattern shape and laminated on a transparent substrate;

an interlayer film having etching properties different from that of the semi-transmissive film and laminated on the semi-transmissive film such that at least a portion of a peripheral region of the semi-transmissive film is exposed;

A light-shielding film having a predetermined pattern shape and etching characteristics identical to those of the semi-transmissive film and stacked on the intermediate film is provided;

At least a part of the exposed portion of the semi-transmissive film is provided with a gradation portion composed of a plurality of regions in which transmittance is increased step by step toward the edge of the semi-permeable film.

It is a multi-gradation photomask.

Here, as an aspect of the method for manufacturing a multi-gradation photomask according to the present invention,

The intermediate preparation process includes an intermediate preparation process for preparing the intermediate;

The intermediate manufacturing process is

A resist film forming process of forming a resist film on the surface of photo mask blanks;

a resist pattern forming step of forming a predetermined resist pattern;

A light-shielding film etching step of etching and removing the exposed portion of the light-shielding film using the resist pattern as a mask;

Using the light-shielding film as a mask, the intermediate film surface etching is performed by etching and removing a portion of a predetermined depth in the film thickness direction among the exposed portions of the intermediate film; A shaping process of forming the part of the intermediate film into a shape in which the edge spreads outward (wider) as it approaches the transparent substrate by alternately repeating the light-shielding film side etching in which the depth portion is etched and removed a plurality of times;

A semi-transmissive film etching step of etching and removing the exposed portion of the semi-transmissive film using the intermediate film as a mask;

A resist film removal step of removing the resist film, comprising:

configuration can be employed.

Also, in this case,

The shaping process is to shape the corresponding part of the interlayer into a stepped shape.

configuration can be employed.

In addition, as another aspect of the method for manufacturing a multi-gradation photomask according to the present invention,

The number of interlayer film surface etching and light shielding film side etching is set based on the number of gradations in the gradation part.

configuration can be employed.

In addition, as another aspect of the method for manufacturing a multi-gradation photomask according to the present invention,

the etching amount of each interlayer film surface etching is set so that the sum of the etching amounts of each interlayer film surface etching is equal to the film thickness of the intermediate film or larger than the film thickness of the intermediate film by a predetermined size

configuration can be employed.

In addition, as another aspect of the method for manufacturing a multi-gradation photomask according to the present invention,

The etching amount of each light shielding film side etching is set based on the transmittance gradient of the gradation part.

configuration can be employed.

In addition, as another aspect of the method for manufacturing a multi-gradation photomask according to the present invention,

The position of the edge of the portion corresponding to the gradation portion of the resist pattern is the sum of the film thicknesses of the semi-transmissive film, the intermediate film, and the light-shielding film, or a predetermined size higher than the total value with respect to the position of the edge of the semi-transmissive film after the semi-transmissive film etching process. A position that is offset outward by a large value

configuration can be employed.

In addition, as another aspect of the method for manufacturing a multi-gradation photomask according to the present invention,

As the intermediate film, a film having an etching rate lower than that of the semi-transmissive film and the light-shielding film is selected.

configuration can be employed.

In addition, as another aspect of the method for manufacturing a multi-gradation photomask according to the present invention,

The number of interlayer division etching and plasma processing is set based on the number of gradations in the gradation part.

configuration can be employed.

In addition, as another aspect of the method for manufacturing a multi-gradation photomask according to the present invention,

The processing time of each plasma treatment is set based on the transmittance gradient of the gradation part.

configuration can be employed.

In addition, as an aspect of the multi-gradation photomask according to the present invention,

When the edge of the interlayer film goes inward than the edge of the light-shielding film, an undercut in which the interlayer film does not exist is formed below the edge of the light-shielding film.

configuration can be employed.

In addition, as another aspect of the multi-gradation photomask according to the present invention,

The thickness of the interlayer film is not less than 90 nm and not more than 200 nm.

configuration can be employed.

According to the present invention, the drawing process may be performed once. Accordingly, alignment is not required in the manufacturing process of the multi-gradation photomask. Therefore, according to the present invention, there is no misalignment and high-definition multi-gradation photomask can be realized.

1 is an enlarged cross-sectional view of a main part of a multi-gradation photomask according to an embodiment of the present invention.
2(a) to (d) are explanatory views of a method of manufacturing a multi-gradation photomask.
3(a) to (d) are explanatory views following FIG. 2 .
4(a) to (d) are explanatory views following FIG. 3 .
5(a) to (d) are explanatory views following FIG. 4 .
6(a) to (c) are explanatory views following FIG. 5 .
7(a) to (c) are explanatory diagrams of plasma irradiation time in the plasma processing step.
8 is an explanatory diagram showing the relationship between the position of the edge of the semi-transmissive film and the position of the edge of the resist film.
Fig. 9 is an explanatory diagram showing the relationship between the position of the edge of the light-shielding film and the position of the edge of the resist film;
Fig. 10 is an explanatory diagram showing the relationship between the position of the edge of the light-shielding film and the position of the boundary of the gradation part.
11(a) and 11(b) are explanatory diagrams regarding the transmittance gradient in the gradation part.
12A and 12B are explanatory views showing the relationship between the position of the edge of the light-shielding film and the position of the edge of the intermediate film.
Fig. 13(a) is an enlarged cross-sectional view of main parts of an island type (convex type) multi-gradation photomask. Fig. 13(b) is an enlarged cross-sectional view of a main part of a hole-type (concave-type) multi-gradation photomask.
14(a) to 14(d) are explanatory views of another manufacturing method of a multi-gradation photomask.
15(a) to 15(d) are explanatory views following FIG. 14 .
16(a) to 16(d) are explanatory views of another method of manufacturing a multi-gradation photomask.
17(a) to 17(d) are explanatory views following FIG. 16 .

First, the configuration of a multi-gradation photomask according to an embodiment of the present invention will be described.

As shown in FIG. 1 , the multi-gradation photomask 1 includes a transmissive part 20 , a transflective part 30 and a light blocking part 50 , and a gradation part 31 in the transflective part 30 . It is a gradient mask. The gradation part 31 is composed of a plurality of regions in which the transmittance is increased step by step toward the boundary between the transflective part 30 and the transmissive part 20 (towards the edge 3a of the transflective film 3 ). In the present embodiment, the gradation portion 31 has three regions: an innermost portion 31C, one intermediate portion 31B, and an outermost portion 31A from the light shielding portion 50 toward the transmissive portion 20 . (3 gradations). Accordingly, in the present embodiment, the multi-gradation photomask 1 has 5 gradations.

The multi-gradation photomask 1 is manufactured from a photomask blank in which a semi-transmissive film 3, an intermediate film (etch stopper film) 4 and a light-shielding film 5 are laminated in this order on a transparent substrate 2 . Because the semi-permeable film 3 is in the lowermost layer, this photomask blank is called a bottom type.

In the photomask blank, the semi-transmissive film 3 is formed on the transparent substrate 2 by a sputtering method, a vapor deposition method, or the like. The film thickness of the semi-transmissive film 3 is, for example, in the range of 10 nm to 50 nm. The intermediate film 4 is formed on the semi-transmissive film 3 by a sputtering method, a vapor deposition method, or the like. The film thickness of the intermediate film 4 is, for example, in the range of 90 nm to 200 nm. The reason for this will be described later. The light-shielding film 5 is formed on the intermediate film 4 by a sputtering method, a vapor deposition method, or the like. The film thickness of the light shielding film 5 is, for example, in the range of 50 nm to 120 nm.

The transparent substrate 2 is a substrate such as synthetic quartz glass. The transparent substrate 2 has a transmittance of 95% or more with respect to a representative wavelength (eg, i-line, h-line, or g-line) included in the exposure light used in the drawing process using the multi-gradation photomask 1 . . The exposure light may be, for example, i-line, h-line, or g-line, or may be mixed light containing at least two of these lights. However, exposure light is not limited to these.

For the semi-permeable film 3, a Cr-based material is used among known materials such as Cr or Cr-based compound, Ni or Ni-based compound, Ti or Ti-based compound, Si-based compound, and metal silicide compound. In this embodiment, a Cr-based compound is used for the semi-permeable film 3 . The semi-permeable membrane 3 is a halftone membrane. Alternatively, the semitransmissive film 3 may be a phase shift film. The semi-transmissive film 3 has a transmittance lower than the transmittance of the transparent substrate 2 and higher than the transmittance of the light-shielding film 5 with respect to a representative wavelength included in the exposure light, and has a transmittance of 10% to 70% with respect to the representative wavelength. It is set so that it becomes the transmittance|permeability.

For the interlayer film 4, a non-Cr-based material is used. In this embodiment, Ni, Ti, or a molybdenum silicide compound is used for the interlayer film 4 .

The light shielding film 5 is made of the same material as the semi-transmissive film 3 . In the present embodiment, a Cr-based compound is used for the light-shielding film 5 . The light shielding film 5 has a transmittance of 1% or less with respect to a representative wavelength included in the exposure light. Alternatively, even if the transmittance of the light-shielding film 5 is higher than 1%, the laminate transmittance in the light-shielding portion 50 may be 1% or less. Alternatively, the optical density (OD value) of the light blocking unit 50 may satisfy 2.7 or more.

The semi-transmissive film 3 and the light-shielding film 5 have the same etching characteristics because the same material is used. However, since the materials of the semi-transmissive film 3 and the light-shielding film 5 and the intermediate film 4 are different, the etching properties are different. That is, the semi-transmissive film 3 and the light-shielding film 5 have etching selectivity with respect to the intermediate film 4 , and the intermediate film 4 has etching selectivity with respect to the semi-transmissive film 3 and the light-shielding film 5 .

The light-shielding portion 50 is a region in which the semi-transmissive film 3 , the intermediate film 4 and the light-shielding film 5 are not removed, that is, a region in which the light-shielding film 5 up to the edge 5a of the light-shielding film 5 is present. is equivalent to The transflective part 30 is provided between the light blocking part 50 and the transmissive part 20 . The semi-transmissive portion 30 is a region where the intermediate film 4 and the light-shielding film 5 are removed from the photomask blank to expose the semi-transmissive film 3 , that is, from the edge 5a of the light-shielding film 5 . It corresponds (corresponds) to the area|region where the semi-permeable film|membrane 3 up to the edge 3a of was exposed. The transmissive part 20 is a region where the transmissive film 3, the intermediate film 4, and the light blocking film 5 are removed from the photomask blank and the transparent substrate 2 is exposed, that is, the edge 3a of the semi-transmissive film 3 Corresponds to the area where the transparent substrate 2 is exposed.

The gradation part 31 is provided throughout the transflective part 30 . The innermost part 31C of the gradation part 31 is a region located at the innermost side and in contact with the light-shielding part 50 , that is, from the edge 5a of the light-shielding film 5 to the boundary 3c within the semi-transmissive film 3 . corresponding to the area. The middle portion 31B of the gradation portion 31 is a region between the innermost 31C and the outermost 31A of the gradation portion 31, that is, from the boundary 3c in the semi-transmissive film 3 to the boundary 3b. It corresponds to the area up to The outermost part 31A of the gradation part 31 is located at the outermost part and is in contact with the transmissive part 20, that is, from the boundary 3b within the semi-transmissive film 3 to the edge 3a of the semi-transmissive film 3 . corresponds to the area of In addition, in this embodiment, since the gradation part 31 is three gradations, the middle part 31B is one. However, when the gradation part 31 has 4 gradations, two intermediate parts 31B are provided, etc., if the number of gradations in the gradation part 31 is n, the number of intermediate parts 31B is n-2. .

The edge 4a of the interlayer film 4 goes inward than the edge 5a of the light-shielding film 5, and the lower side of the edge 5a of the light-shielding film 5 becomes an undercut 4b where the interlayer film 4 does not exist. have. And in addition to this, the edge part of the light shielding film 5 overhangs and becomes the protruding edge part 5b.

Although not shown, in the laminated film structure shown in FIG. 1 , the light blocking film 5 is also provided symmetrically on the opposite side in a state in which it has a predetermined width. Then, one pattern 1A is constituted by the light-shielding portion 50 and the semi-transmissive portions 30 and 30 (gradation portions 31 and 31) on both sides.

Next, a method for manufacturing the multi-gradation photomask 1 according to an embodiment of the present invention will be described.

The manufacturing method of the multi-gradation photomask 1 includes: i) a resist film forming step (step 1), ii) a drawing step (step 2), iii) a developing step (step 3), iv) a light-shielding film etching step ( Step 4), v) Interlayer surface etching step (Step 5), vi) Light-shielding film side etching step (Step 6), vii) Semi-transmissive film etching step (Step 7), viii) Resist film removal step (Step 8), ix ) interlayer film division etching step (step 9) and x) plasma treatment step (step 10). In addition, the drawing process (process 2) and the developing process (process 3) are collectively referred to as a resist pattern formation process, and the intermediate film surface etching process (process 5) and light-shielding film side etching process (process 6) are collectively referred to as a shaping process.

In the resist film forming step (step 1), as shown in Fig. 2(a), a resist is uniformly applied to the surface of a photomask blank to form a resist film 6 . The resist is applied by a coating method or a spray method.

In the writing process (process 2), as shown in FIG.2(b), exposure light is irradiated to the surface of the resist film 6 using the electron beam or laser of a writing apparatus (exposure apparatus), and a predetermined resist pattern is formed. is painted The details of the design of the resist pattern (the design position of the edge 6a of the resist film 6) will be described later. In the developing process (process 3), as shown in FIG.2(c), the excess part 6b of the resist film 6 is removed, and a resist pattern is formed. The development is carried out by immersion in a developer.

In the light-shielding film etching step (Step 4), as shown in Fig. 2(d), the exposed portion 5c of the light-shielding film 5 is etched and removed using the resist pattern as a mask for etching processing. The etching may be either dry etching or wet etching, but wet etching is preferable if it is a large-sized photomask. An etchant or an etching gas is used as the etchant. In any etchant, only the light-shielding film 5 is selectively etched because an etchant having an etching selectivity to the light-shielding film 5 (an etchant that does not etch the intermediate film 4) is used.

In addition, in the light-shielding film etching step (Step 4), the etching amount is excessively etched with respect to the etching amount corresponding to the film thickness of the light-shielding film 5 so that the unetched light-shielding film 5 does not remain on the surface of the intermediate film 4 . To increase, so-called overetching is performed.

In the intermediate film surface etching step (step 5), as shown in Fig. 3(a) , the light shielding film 5 is used as a mask for the etching process, and among the exposed portions of the intermediate film 4, a predetermined depth in the film thickness direction is formed. A portion (surface portion) 4c is removed by surface etching. The etching may be either dry etching or wet etching, but wet etching is preferable if it is a large-sized photomask. As the etchant, an etching liquid or an etching gas is used. Since either an etchant having an etching selectivity for the intermediate film 4 (an etchant that does not etch the light-shielding film 5) is used, only the intermediate film 4 is selectively etched.

The material of the intermediate film 4 and/or the etchant of the intermediate film 4 is selected such that the etching rate of the intermediate film 4 is low. Thereby, only the surface portion 4c of the intermediate film 4 can be etched. In addition, by selecting an appropriate etching rate, it is possible to appropriately control the etching amount (the film reduction amount of the intermediate film 4).

The interlayer film surface etching step (step 5) is performed a plurality of times as shown in FIGS. 3(a), 3(c), 4(a) and 4(c) (steps 5-1, 5- 2, 5-3, 5-4). The number of times of the interlayer film surface etching process (step 5) is (the number of gradations in the gradation part 31 + 1) times. In this embodiment, since the gradation part 31 has three gradations, the number of times of the interlayer film surface etching process (Step 5) is four times.

In the light-shielding film side etching process (process 6), as shown in FIG.3(b), a predetermined depth (predetermined width) part of the light-shielding film 5 in the inward direction from the end surface of the exposed edge 5a. (5d) is side etched and removed. The side etching is performed by the same method and the same etchant as the light-shielding film etching step (step 4).

The light shielding film side etching step (step 6) is performed multiple times as shown in Figs. 3(b), 3(d) and 4(b) (steps 6-1, 6-2, 6-3). . The number of times of the light shielding film side etching process (Step 6) is the same as the number of gradations of the gradation part 31 . In other words, the number of times of the light-shielding film side etching process (step 6) is (number of times of the interlayer film surface etching step (step 5)-1). In this embodiment, since the gradation part 31 has 3 gradations, and the number of times of the interlayer film surface etching process (process 5) is 4 times, the number of times of the light-shielding film side etching process (process 6) is 3 times. In addition, in FIG.3(b), FIG.3(d), and FIG.4(b), the etching amount of side etching is briefly described in relation to the width size of the paper. The actual image is close to that described in FIG. 9 .

The interlayer film surface etching step (Step 5) and the light shielding film side etching step (Step 6) are alternately repeated a plurality of times, starting and ending the interlayer film surface etching step (Step 5). In the present embodiment, step 5-1, step 6-1, step 5-2, step 6-2, step 5-3, step 6-3, step 5-4 is performed in the order. As the surface etching of the intermediate film 4 and the side etching of the light-shielding film 5 are alternately repeated a plurality of times, the exposed portion of the intermediate film 4 has a shape that spreads outward as it approaches the transparent substrate 2 . More specifically, the exposed portion of the interlayer film 4 has a step shape.

Each of steps 5-1, 5-2, 5-3, and 5-4 of the intermediate film surface etching step (step 5) is an etching amount divided so that the sum of the etching amounts in each step becomes the film thickness of the intermediate film 4 . is carried out Preferably, each step is performed by an etching amount obtained by dividing the film thickness of the interlayer film 4 by the number of interlayer film surface etching steps (step 5). For example, if the film thickness of the intermediate film 4 is 100 nm and the number of times of the intermediate film surface etching process (step 5) is 4, the etching amount per one time will be 25 nm. However, it is not essential that the etching amount of each process is the same. The etching amount of each process may differ. In any case, as described above, since the etching rate of the intermediate film 4 is low, such fine surface etching becomes possible. However, when the total etching amount is equal to the film thickness, there is a risk that the unetched interlayer film 4 remains on the surface of the semi-transmissive film 3 . Therefore, overetching is performed in the last interlayer film surface etching step (step 5-4). It is for this reason that the etching amount described in FIG.4(c) is larger than the etching amount described in FIG.3(a), FIG.3(c), and FIG.4(a).

Each of the steps 6-1, 6-2, and 6-3 of the light-shielding film side etching process (Step 6) corresponds to the transmittance gradient of the gradation part 31 and is directed to the design position of the edge 5a of the light-shielding film 5 . It is performed by dividing the etching amount.

In the semi-transmissive film etching step (Step 7), as shown in Fig. 4(d) , the intermediate film 4 is used as a mask for the etching process, and the exposed portion 3d of the semi-transmissive film 3 is etched and removed. . Etching is performed by the same method as the light-shielding film etching process (Step 4) or the light-shielding film side etching process (Step 6), and the same etchant. Further, since the etchant used has etching selectivity for the light-shielding film 5 and the semi-transmissive film 3, not only the exposed portion 3d of the semi-transmissive film 3 is etched, but also exposed in the light-shielding film 5 A portion 5d of the same amount in the inward direction from the cross section of the edge 5a is side-etched.

In addition, in the semi-transmissive film etching step (Step 7), the etching amount corresponding to the film thickness of the semi-transmissive film 3 is adjusted so that the unetched semi-transmissive film 3 does not remain on the surface of the transparent substrate 2 . On the other hand, overetching to increase the etching amount excessively is performed.

In the resist film removal step (Step 8), the resist film 6 is removed as shown in Fig. 5A. The resist film 6 is removed by an ashing method or immersion in a resist stripping solution.

Through the above steps 1 to 8, the intermediate body of the multi-gradation photomask 1 is completed. As shown in Fig. 5(a), the intermediate body includes a semi-transmissive film 3 having a predetermined pattern shape laminated on a transparent substrate 2, an intermediate film 4 laminated so as to overlap on the semi-transmissive film 3, A light shielding film 5 having a predetermined pattern shape is laminated on the intermediate film 4 so that at least a portion of the peripheral region of the intermediate film 4 is exposed, wherein at least a part of the exposed portion of the intermediate film 4 is formed on the transparent substrate 2 ), the edge 4a has a shape that spreads outward (a direction away from the light-shielding film 5 in the plane direction), and has these laminated film structures. More specifically, at least a part of the exposed portion of the interlayer film 4 has a step shape in which the edge 4a spreads outward as it approaches the transparent substrate 2 . The number of steps is the same as the number of gradations of the gradation unit 31 . In this embodiment, since the gradation part 31 has three gradations, the number of stages is three (lower part 4d, middle part 4e, upper part 4f). . Subsequent steps 9 and 10 are steps for the prepared intermediate.

In the intermediate film division etching step (step 9), as shown in Fig. 5(b) , the light shielding film 5 is used as a mask for etching, and a predetermined depth in the film thickness direction is formed among the exposed portions of the intermediate film 4 . A portion (surface portion) 4c is removed by surface etching. The surface etching is performed by the same method and the same etchant as the intermediate film surface etching step (Step 5). As the etchant is an etchant having etching selectivity for the intermediate film 4 (etchants that do not etch the semi-transmissive film 3 and the light-shielding film 5), only the intermediate film 4 is selectively etched.

In addition, in the intermediate film division etching process (step 9), the etching rate of the intermediate film 4 is low, similarly to the intermediate film surface etching process (step 5). Thereby, only the surface portion 4c of the intermediate film 4 can be etched. In addition, by selecting an appropriate etching rate, it is possible to appropriately control the etching amount (the film reduction amount of the intermediate film 4).

The intermediate film division etching process (Step 9) is performed a plurality of times as shown in Figs. 5(b), 5(d) and 6(b) (Steps 9-1, 9-2, 9-3). . The number of times of the intermediate film division etching process (step 9) is the same as the number of stages of the intermediate film 4 (that is, the number of gradations of the gradation part 31 ). In the present embodiment, since the number of stages of the intermediate film 4 is three, the number of times of the intermediate film division etching process (step 9) is three.

In the plasma processing process (process 10), as shown in FIG.5(c), plasma is irradiated to the surface of the exposed part of the semi-transmissive film|membrane 3 by a plasma processing apparatus. The plasma processing apparatus may be any of an apparatus for performing surface treatment by generating plasma under atmospheric pressure (atmospheric pressure plasma processing apparatus), and an apparatus for performing surface treatment by generating plasma under reduced pressure in a closed chamber (reduced pressure plasma processing apparatus) , if it is a large-sized photomask, an atmospheric pressure plasma processing apparatus is preferable.

Transmittance of the semi-permeable membrane 3 irradiated with plasma changes (increases) according to the irradiation time. On the other hand, since the portion of the semi-transmissive film 3 covered with the intermediate film 4 is not affected by the plasma treatment, the transmittance does not change. Accordingly, the interlayer film 4 functions as a mask for plasma processing.

The plasma treatment step (step 10) is performed a plurality of times (steps 10-1 and 10-2) as shown in Figs. 5(c) and 6(a). The number of times of the plasma treatment step (step 10) is (number of gradations in the gradation unit 31 - 1). In other words, the number of times of the plasma treatment step (step 10) is (number of interlayer film division etching steps (step 9) minus 1). In the present embodiment, since the gradation part 31 has three gradations, and the number of times of the interlayer division etching process (step 9) is 3 times, the number of times of the plasma processing step (step 10) is 2 times.

The intermediate film division etching process (Step 9) and the plasma treatment process (Step 10) are alternately repeated a plurality of times, starting and ending the intermediate film division etching process (Step 9). In the present embodiment, step 9-1, step 10-1, step 9-2, step 10-2, step 9-3 is performed in the order.

The first intermediate film division etching step (Step 9-1) is performed with an etching amount corresponding to the film thickness of the lower end portion 4d of the intermediate film 4 . Accordingly, in the first intermediate film division etching step (Step 9-1), the lower end portion 4d of the intermediate film 4 is removed. For this reason, in the first plasma treatment step (Step 10-1), the lower end 4d of the intermediate film 4 is removed, so that the surface of the exposed portion of the semi-transmissive film 3 is irradiated with plasma, The penetration rate is increased.

The second interlayer divided etching step (Step 9-2) is an etching corresponding to the film thickness of the middle portion 4e of the intermediate film 4 lowered in height by the first interlayer divided etching step (Step 9-1). performed in quantity. Thereby, in the second intermediate film division etching process (Step 9-2), the middle portion 4e of the intermediate film 4 is removed. For this reason, in the second plasma treatment step (step 10-2), the lower end 4d of the intermediate film 4 is removed, thereby further irradiating the surface of the exposed portion of the semi-transmissive film 3 with plasma, As the transmittance of the portion is further increased, plasma is irradiated to the surface of the exposed portion of the semi-permeable film 3 by removing the intermediate portion 4e of the intermediate film 4, thereby increasing the transmittance of the portion. Thereby, the outermost part 31A of the gradation part 31 with the highest transmittance|permeability, and the intermediate part 31B with the highest transmittance|permeability next to the outermost part 31A are formed.

In the third interlayer divided etching process (Step 9-3), the etching amount corresponding to the film thickness of the upper end portion 4f of the intermediate film 4 lowered in height by the second interlayer divided etching step (Step 9-2) is performed with As a result, in the third intermediate film division etching step (Step 9-3), the upper end portion 4f of the intermediate film 4 is removed. The innermost portion 31C of the gradation portion 31 is an exposed portion of the semi-transmissive film 3 by removing the upper portion 4f of the intermediate film 4 . The innermost part 31C is not subjected to plasma treatment. For this reason, the transmittance|permeability of the innermost part 31C is the same as the transmittance|permeability of the semi-transmissive film|membrane 3, and is the lowest transmittance|permeability among the gradation parts 31. As shown in FIG.

As mentioned above, the transmittance|permeability of each part 31A, 31B, 31C of the gradation part 31 has a correlation with the integrated value of plasma irradiation time. As shown in Fig. 7(a), the irradiation time S2 is required to set the transmittance of the outermost part 31A to T3, and the irradiation time S1 is required to set the transmittance of the middle part 31B to T2. If necessary, plasma is irradiated so that the irradiation time becomes (S2-S1) in the first plasma treatment step (step 10-1), and in the second plasma treatment step (step 10-2), the irradiation time is S1 Plasma is irradiated as much as possible. In this way, the irradiation time in each of steps 10-1 and 10-2 of the plasma treatment step (step 10) is obtained based on the transmittance of the respective portions 31A, 31B, and 31C of the gradation portion 31 .

Then, by appropriately setting the irradiation time in each of steps 10-1 and 10-2 of the plasma treatment step (step 10), the transmittance gradient of the gradation unit 31 can be appropriately set. For example, the example shown in FIG.7(a) is an example in which the transmittance|permeability gradient of the gradation part 31 becomes linear by equalizing the irradiation time in each process 10-1, 10-2. In addition, the example shown in FIG.7(b) is an example in which the irradiation time in process 10-2 becomes longer than the irradiation time in process 10-1, and the transmittance|permeability gradient of the gradation part 31 becomes a curve. The example shown in Fig. 7(c) is an example in which the irradiation time in step 10-2 is shorter than the irradiation time in step 10-1, and the transmittance gradient of the gradation part 31 becomes a curve.

In each step 9-1, 9-2, and 9-3 of the intermediate film division etching step (step 9), overetching is performed so that the unetched interlayer film 4 does not remain on the surface of the semi-transmissive film 3 . is carried out The etching amount described in FIG. 5(b) is larger than the film thickness of the lower end portion 4d of the intermediate film 4, and the etching amount described in FIG. It is more than the film thickness, and it is for this reason that the etching amount described in FIG.6(b) is larger than the film thickness of the upper end part 4f of the intermediate film 4 with a reduced film thickness.

Through the above steps 1 to 9-3, as shown in FIG. 6(c) (and FIG. 1), the multi-gradation photomask 1 is completed. According to the manufacturing method of the multi-gradation photomask 1 which concerns on this embodiment, a drawing process may be just once. Therefore, alignment becomes unnecessary in the manufacturing process of a multi-gradation photomask. Therefore, according to the manufacturing method of the multi-gradation photomask 1 which concerns on this embodiment, and the multi-gradation photomask 1, there is no alignment shift, and for this reason, a lead time can be shortened, and high-precision multi-gradation. A photomask can be manufactured.

In addition, the conditions of the manufacturing method of the multi-gradation photomask 1 are roughly as follows.

・Process temperature of each etching step (Step 4 to Step 7, Step 9): 20°C to 24°C (for example, 23°C)

・Process time of the light-shielding film etching step (step 4): 60 seconds to 200 seconds

-Process time per process of each etching process (process 5, process 9) of the intermediate film 4: 5 minutes to 10 minutes

・Process time per step of the light-shielding film side etching step (step 6): 500 seconds to 2000 seconds

・Process time of the semi-transmissive film etching step (Step 7): 20 seconds to 100 seconds

- Incidentally, each etching rate of the semi-transmissive film 3 and the light shielding film 5 is about 1 nm/sec as an example, and the etching rate of the intermediate film 4 is about 4 nm/min as an example.

Next, the details of the design of the resist pattern (the design position of the edge 6a of the resist film 6), which were dealt with in the description part of the drawing process (step 2), will be described.

It is in the semi-transmissive film etching process (step 7) that the position of the edge 3a of the semi-transmissive film 3 is finished at the design position. Here, the relationship between the design position of the edge 6a of the resist film 6 and the design position of the edge 3a of the semi-transmissive film 3 is shown in FIG. As can be seen from FIG. 8 , the difference A between the two is expressed by the following equation. Further, in each of the above etching steps, it is assumed that each of the semi-transmissive film 3, the intermediate film 4, and the light-shielding film 5 is etched at the same rate (etch rate) in the film thickness direction and the inward direction (hereinafter referred to as the etching rate). , same here).

Difference A = film thickness of semi-permeable film 3 FT3 + overetching amount OE3 in step 7

+ Film thickness FT4 of the intermediate film 4 + Over-etching amount OE4 in step 5

+ Film thickness FT5 of light-shielding film 5 + Over-etching amount OE5 in step 4

Therefore, the design position of the edge 6a of the resist film 6, that is, the writing data of the resist pattern, is outwardly offset by a difference A with respect to the design position of the edge 3a of the semi-transmissive film 3 become data.

It is also in the semi-transmissive film etching process (step 7) that the position of the edge 5a of the light-shielding film 5 is finished at the design position. Here, the relationship between the design position of the edge 6a of the resist film 6 and the design position of the edge 5a of the light shielding film 5 is shown in FIG. As can be seen from FIG. 9 , the difference B between the two is expressed by the following equation.

Difference B = film thickness of semi-permeable film 3 FT3 + overetching amount OE3 in step 7

+ Total side etching amount in process 6 (SE5-1~3)

+ Film thickness of light shielding film 5 FT5 + Over-etching amount OE5 in step 4

Therefore, based on this formula, by appropriately setting the side etching amount in each step 6-1, 6-2, 6-3 of the light-shielding film side etching step (step 6), the edge 5a of the light-shielding film 5 is The location can be finished at the design location.

Next, the transmittance|permeability gradient of the gradation part 31 is demonstrated.

The upper view of FIG. 10 shows the change of the laminated film structure of the photomask blank by the intermediate film surface etching process (Step 5) and the light-shielding film side etching process (Step 6), and the lower view of FIG. 10 shows the multi-gradation photomask 1 ), and both figures are described in a state where the positions in the plane direction are merged in the vertical direction. As can be seen from this, the position of the stepwise edge 5a of the light-shielding film 5 by the light-shielding film side etching process (Step 6), the edge 4a of the intermediate film 4, and each end 4d, 4e, Although the position of the boundary of 4f) is slightly shifted due to the occurrence of side etching of the respective ends 4d, 4e, and 4f of the intermediate film 4, it can be seen that there is a correlation. Further, the position of the edge 4a of the intermediate film 4 and the boundary of the respective ends 4d, 4e, 4f, the edge 3a of the gradation portion 31 and the boundary 3b, 3c of the gradation portion 31 Although the positions are slightly shifted due to the occurrence of side etching of the respective ends 4d, 4e, and 4f of the intermediate film 4, it can be seen that there is a correlation. And, from these, the position of the edge 5a of the light shielding film 5 stepwise by the light shielding film side etching process (step 6), the edge 3a of the gradation part 31, and the boundary 3b of the gradation part 31 , 3c) is slightly shifted due to the occurrence of side etching of the respective ends 4d, 4e, and 4f of the intermediate film 4, but it can be seen that there is a correlation.

Therefore, the transmittance|permeability gradient of the gradation part 31 can be set suitably by setting the side etching amount in each process 6-1, 6-2, 6-3 of the light shielding film side etching process (process 6) suitably. For example, the example shown in the lower drawing of FIG. 10 (and FIG. 1) is an example in which the transmittance|permeability gradient of the gradation part 31 becomes linear by equalizing the side etching amount. In the example shown in Fig. 11A, the width of the region gradually widens toward the edge 3a of the semi-transmissive film 3, and the transmittance gradient of the gradation portion 31 becomes a curve. Further, the example shown in FIG. 11(b) is an example in which the width of the region gradually becomes narrower toward the edge 3a of the semi-transmissive film 3, and the transmittance gradient of the gradation portion 31 becomes a curve.

Next, the film thickness of the intermediate film 4 dealt with in the description part of the photomask blank is demonstrated.

12, the amount of overhang of the protruding end 5b of the light shielding film 5 is expressed by the following equation.

Overhang amount = film thickness FT4 of the interlayer film 4

- {film thickness FT4/(number of gradations in the gradation part 31 + 1)

+ Over-etching amount OE4 in step 5}

+ Over-etching OE4 in process 9-3

From this equation, the film thickness FT4 of the interlayer film 4 is expressed by the following equation.

Film thickness FT4 = (Overhang amount + Over-etching amount OE4 in step 5)

- Over-etching OE4 in process 9-3)

/ {1 - 1/(number of gradations in the gradation unit 31 + 1)}

Here, the amount of overhang is preferably 150 nm or less in order to prevent deformation due to sagging of the protruding end portion 5b. Then, when each overetching amount OE4 is 15 nm and the gradation part 31 is 3 gradations, the film thickness of the intermediate film 4 is 200 nm or less.

Next, in the lower limit of the film thickness of the intermediate film 4, in order to form an appropriate gradation portion 31, the film of the intermediate film 4 in the intermediate film surface etching process (Step 5) and the intermediate film division etching process (Step 9) Thickness control becomes important. When the etching rate is too high, it becomes difficult to control the film thickness of the intermediate film 4 . Conversely, if the etching rate is too low, the process takes time and productivity is lowered. Therefore, the etching rate is about 4 nm/min, and the process time per step of the intermediate film surface etching step (Step 5) and the intermediate film divided etching step (Step 9) is preferably about 7.5 minutes.

Then, the film thickness FT4 of the intermediate film 4 is expressed by the following equation.

Film thickness FT4 = (number of gradations in the gradation section 31 + 1) Х 30 nm

From the above, by setting the film thickness of the intermediate film 4 in the range of 90 nm to 200 nm, the gradation part 31 of 2 to 5 gradations (that is, a high-precision multi-gradation photomask having 4 to 7 gradations) can be manufactured. have.

Next, the entire pattern of the multi-gradation photomask 1 will be described.

As an example, the unit pattern 1A of the multi-gradation photomask 1 has a form in which the semi-transmissive portion 30 (the gradation portion 31 ) is provided over the entire peripheral region of the light-shielding portion 50 . 13(a) shows a plurality of unit patterns 1A, ... It is an island type (convex type) multi-gradation photomask 1 in which the distances are widened from each other (by making the area of the transmission part 20 sufficiently wide) and arranged at a two-dimensionally constant pitch (pitch, spacing). 13(b) shows a plurality of unit patterns 1A in which the area of the light-shielding portion 50 is sufficiently wide, ... It is a hole type (concave type) multi-gradation photomask 1 which is arranged at regular pitch by approaching each other (by narrowing the area of the transmission part 20 sufficiently).

In addition, this invention is not limited to the said embodiment, Various changes are possible in the range which does not deviate from the summary of this invention.

In the above embodiment, the multi-gradation photomask has 5 gradations. However, the present invention is not limited thereto. A multi-gradation photomask of 6 or more gradations can be manufactured by setting the number of steps of the interlayer film to 4 or more (the middle part is 2 or more steps) and forming two or more intermediate parts of the gradation part. Alternatively, a multi-gradation photomask having four gradations can be manufactured by setting the number of steps of the interlayer film to two (no intermediate portions are provided) and not forming the intermediate portions of the gradation portions.

Moreover, in the said embodiment, the gradation part 31 is provided in the whole area of the semi-transmissive part 30, and it coincides with the semi-transmissive part 30. As shown in FIG. However, the present invention is not limited thereto. The gradation part may be provided in a part of the semi-transmissive part.

Moreover, in the said embodiment, the interlayer film surface etching process (process 5) and the light-shielding film side etching process (process 6) are repeated a plurality of times, starting with the interlayer film surface etching process (process 5). However, the present invention is not limited thereto. For example, as shown in FIGS. 14 and 15 , the interlayer film surface etching step (Step 5) and the light-shielding film side etching step (Step 6) are alternated a plurality of times, starting with the light-shielding film side etching step (Step 6). may be repeated. 14 and 15 , the number of interlayer film surface etching steps (step 5) is the same as the number of gradations in the gradation portion 31 . The number of times of the light shielding film side etching step (step 6) is (the number of gradations in the gradation section 31 + 1) times. In other words, the number of times of the light shielding film side etching process (process 6) is (the number of times of the interlayer film surface etching process (process 5) +1).

Moreover, in the said embodiment and the example of FIGS. 14 and 15, either one of an interlayer film surface etching process (process 5) and a light-shielding film side etching process (process 6) is one process more. However, the present invention is not limited thereto. For example, as shown in FIGS. 16 and 17 , the interlayer film surface etching step (step 5) and the light shielding film side etching step (step 6) may have the same number of steps regardless of which one is started.

Further, in the above embodiment, the plasma treatment step (Step 10) is performed after the first interlayer divided etching step (Step 9-1) and the second interlayer divided etching step (Step 9-2). However, the present invention is not limited thereto. The plasma treatment step (step 10) may be performed even after the last interlayer divided etching step.

In addition, in this invention, instead of a light shielding film, a phase shift film|membrane may be sufficient. The optical density (OD value) should just be 2.7 or more by lamination|stacking with the semi-transmissive film|membrane of the lower layer.

One… Multi-gradation photomask, 1A… pattern, 2… Transparent substrate, 20 ... Transmissive part, 3... semipermeable membrane, 3a... edge, 3b... Boundary, 3c... border, 3d... Part, 30… transflective section, 31 . . . Gradient part, 31A... Outermost, 31B… Middle part, 31C... innermost, 4… Intermediate film (etch stopper film), 4a... edge, 4b... Undercut, 4c... part (surface part), 4d... lower part, 4e... Interruption, 4f... upper part, 5... shading film, 5a... edge, 5b... protruding end, 5c... Part, 5d… Part, 50... shading part, 6... resist film, 6a... edge, 6b... surplus

Claims (13)

A method for manufacturing a multi-gradation photomask comprising: a transmissive part, a semi-transmissive part, and a light-shielding part;
A semi-transmissive film having a predetermined pattern shape and laminated on a transparent substrate, an intermediate film having etching characteristics different from that of the semi-transmissive film and stacked so as to overlap the semi-transmissive film, and a predetermined pattern shape and the same etching characteristics as the semi-transmissive film and a light-shielding film laminated on the intermediate film so that at least a portion of the peripheral region of the intermediate film is exposed, and at least a portion of the exposed portion of the intermediate film has a shape in which the edge widens outward as it approaches the transparent substrate. An intermediate preparation process for preparing an intermediate consisting of
an intermediate film division etching process in which the exposed portion of the intermediate film is divided into a plurality of times and etched to be finally removed;
After each etching except the last time or including the last time, plasma treatment of the exposed portion of the semi-permeable film to change the transmittance of the portion is provided,
A method of manufacturing a multi-gradation photomask. According to claim 1,
The intermediate preparation process includes an intermediate preparation process for preparing the intermediate;
The intermediate manufacturing process is
A resist film forming step of forming a resist film on the surface of the photomask blank;
a resist pattern forming step of forming a predetermined resist pattern;
A light-shielding film etching step of etching and removing the exposed portion of the light-shielding film using the resist pattern as a mask;
Using the light-shielding film as a mask, interlayer surface etching for etching and removing a portion of the exposed portion of the intermediate film having a predetermined depth in the film thickness direction, and a predetermined depth inward from the end surface of the exposed edge in the light-shielding film A shaping process of forming the part of the intermediate film into a shape in which the edge is wider outward as it approaches the transparent substrate by alternately repeating the light-shielding film side etching a plurality of times to etch and remove the portion of the
A semi-transmissive film etching step of etching and removing the exposed portion of the semi-transmissive film using the intermediate film as a mask;
A resist film removal step of removing the resist film, comprising:
A method of manufacturing a multi-gradation photomask. 3. The method of claim 2,
The shaping process is to shape the corresponding part of the interlayer into a stepped shape,
A method of manufacturing a multi-gradation photomask. 3. The method of claim 2,
The number of interlayer film surface etching and light shielding film side etching is set based on the number of gradations in the gradation part,
A method of manufacturing a multi-gradation photomask. 3. The method of claim 2,
the etching amount of each interlayer film surface etching is set such that the sum of the etching amounts of each interlayer film surface etching is equal to the film thickness of the intermediate film or larger than the film thickness of the intermediate film;
A method of manufacturing a multi-gradation photomask. 3. The method of claim 2,
The etching amount of each light shielding film side etching is set based on the transmittance gradient of the gradation part,
A method of manufacturing a multi-gradation photomask. 3. The method of claim 2,
The position of the edge of the portion corresponding to the gradation part of the resist pattern is the sum of the film thicknesses of the semi-transmissive film, the intermediate film, and the light-shielding film with respect to the position of the edge of the semi-transmissive film after the semi-transmissive film etching process, or a value greater than this sum. position offset outward,
A method of manufacturing a multi-gradation photomask. According to claim 1,
A film having a lower etching rate than that of the semi-transmissive film and the light-shielding film is selected as the intermediate film,
A method of manufacturing a multi-gradation photomask. According to claim 1,
The number of interlayer division etching and plasma processing is set based on the number of gradations in the gradation part,
A method of manufacturing a multi-gradation photomask. According to claim 1,
The processing time of each plasma treatment is set based on the transmittance gradient of the gradation part,
A method of manufacturing a multi-gradation photomask. A multi-gradation photomask having a transmissive part, a semi-transmissive part, and a light-shielding part, comprising:
A semi-transmissive film having a predetermined pattern shape and laminated on a transparent substrate;
an interlayer film having etching properties different from that of the semi-transmissive film and laminated on the semi-transmissive film such that at least a portion of a peripheral region of the semi-transmissive film is exposed;
A light-shielding film having a predetermined pattern shape and etching characteristics identical to those of the semi-transmissive film and stacked so as to overlap on the intermediate film;
At least a part of the exposed portion of the semi-transmissive film is provided with a gradation portion composed of a plurality of regions in which the transmittance is increased step by step toward the edge of the semi-permeable film,
Multi-gradation photomask. 12. The method of claim 11,
When the edge of the interlayer film goes inward than the edge of the light-shielding film, an undercut in which the interlayer film does not exist is formed below the edge of the light-shielding film.
Multi-gradation photomask. 12. The method of claim 11,
The film thickness of the intermediate film is 90 nm or more and 200 nm or less,
Multi-gradation photomask.

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